T-6 Fuel Selector

[Ken]

A search didn't come up with any clear cut answers, so I'll ask again.

My understanding is that the stock T-6 fuel selector valve uses a cork core and is prone to failure. Here are some questions and I'm open to any/all info that WIXers are willing to share.

1- Are NOS cork replacements available, and, if not, is anyone making new cork pieces?

2- I understand that there is a plastic/teflon replacement. Does this work and are any available?

3- Is any other (modern, reliable) fuel valve approved for installation and, if not, is there one that, while not approved, is a logical replacement that others have had success with? Details, model numbers would be most appreciated.

4- Are there any other tips or tricks to maintaining the stock valve?

I'm just learning about this device and trying to help out a friend. As a single point of failure, this doesn't seem like an ideal setup, but I have a lot to learn. Your input is most appreciated.

[Stoney]

The valve and rods to it are the weak point of the system, I never turned the fuel off to keep the cork wet and always check the U joints on the rods every annual. Also never switch tanks unless your over an airport case it fails so you can make an emergency landing.

[Trey Carroll]

I'm sure someone else can back me up on this, but I'm pretty sure the plastic/teflon cones are illegal. I can certainly be wrong, but I thought they were. I'm sure Rich would know, or any other T-6 mechanic here???

One of the 6's I flew had a fuel selector that was VERY hard to turn. Like Stoney said, all of those U-joints need to be lined up right, and free from hitting anything as they go down in to the center section.

And as for the stickiness of the selector, over time, it naturally wedged itself tighter in the valve because of the way it was shape and lack of usage (meaning airplane doesn't fly hardly at all)

[Taylor Stevenson]

100% what Stoney said...

[51fixer]

The design is pretty strong.
Problems involve storage, assy of the unit and common sense.
The cork cone is attached to a plate with grooves positioned in a precise places with a shaft that extends vertically on center.
There is a plate with stamped ridges that engages the groves above that provides the feel of a detent or stopping place as the selector is rotated. This plate is pushed down by a spring, above it a collar and then a o-ring type seal.
This assy is then inserted into the body of the selector and a lid is placed on top and held in place by a gasket and several screws.
The shaft extends out of the lid and has several small pieces that attach to the shaft that form a slotted U that the linkage from the cockpit interface with.
The issues seem to come from setting up the unit on assy. There are shims that sit on the shaft under the U that adjust the depth of the cork. If the cork is to deep in the housing it is difficult to turn.
IIRC there are a couple manufactures of these and parts seem to bolt together but I'm unsure if all the internal dimensions are exactly the same so intermixing parts could cause an issue.
The teflon and rubber cones need a Field Approval from the FAA by the installer. I don't believe they are STCed or PMAed. If they are we can find out here.
Many years ago I think someone got some kind of approval for some selector, maybe from a B-24? I never heard much about it.
Like anything else on a 60-70 year old piece of machinery, it needs to be looked at each year. Any change in how it operates needs to be looked at.
If you ignore it, some day it'll get your attention but probably at a real bad place in time.

[Forgotten Field]

I never turned the fuel off to keep the cork wet

I agree with everything except what I quoted. First, you need to be able to turn off the valve in emergency procedures as well as shutdown. Second, the way the cork works, if you leave the selector in one position most of the time, you won't be bathing the whole cone in gas due to the way it is made and how the cone rotates in the valve body. You need to rotate this periodically to keep the cork evenly exposed to gas and to be able to keep the cork sealed against the valve body. Keeping it in one spot means one part of the cone is getting soaked while the other side is not. If you take one of these apart, you will find that the the used cork has streaks or rings around the cone face from where dirt or other stuff got caught between the cork and valve body. I think rotating the cone moves the cork through its range of motion and helps prevent this.

I've got a few of the selectors for the L-5 and the last one I opened had a beautiful cork, except for the patches which had deteriorated from the surface of the cone and were dry rotted. It COULD have been made to work with fuel lube, but I got another one. You can owner-manufacture the cork cone for a replacement but there are some gotcha's; #1 it is hard to find the right sized piece of correct quality cork; #2 it is hard to find someone who can put it on a lathe and properly turn it and fit it into the valve body; #3 it takes some doing to get the approval from Uncle Sugar. I know a guy who can help you with 1 and 2 and if you PM me your email, I'll send you his name.

As for teflon, I'll defer to the real licensed mechanics out there. I know some people have done it, but any field approval of such a thing would need some approved data to back it up. I don't know if that is out there available.

[Stoney]

Forgotten
I didn't say never turn it, I said I never turn it off, if I never turned it I would only have 55 gal. of gas.

In other news, the B-24 valve is a great piece of enginneering, but it has 4 positions, L, R, Both and Off. It looks like it would be a straight drop in, but I haven't tried it.

[bdk]

For the field approval of the nylon cone, I understand the hard part is getting the cone to seal since it isn't very flexible like the cork. You may have to do some lapping to get it to work, else the valve may still seep when switched off. The cone angles were designed to use with cork, any substitute material needs to be carefully selected and tested to ensure that all design parameters are met.

Banaire advertises the nylon cones, but they have been listed as "out of stock" for some time now (http://banaire.com/). Last time I talked to Art Jr. there, he recommended that I NOT install one because there had been so many problems (i.e. unhappy customers).

I've often thought this modern valve could be made to work: http://www.andair.co.uk/system/index.html

I've heard of the B-24 valve, but have never seen one. It would still need a field approval though.

I didn't know if my original one was any good or not, so I bought a brand new one from Lance (http://lanceaircraftsupply.com/contact.html) for around $600. Expensive yes, but hassle and uncertainty = zero.

[Ken]

Thank you guys. As this seems like a likely single point of failure, I want to learn these tips.

Just curious, is there a source for the B-24 valve in case we wanted to examine one? I'm not sure how tough the FSDO paperwork would be, but, assuming you could substitute a better design or more modern valve; that's a no-brainer for safety. Having said that, I have worked with the gov't and understand that there is a concept called "red tape". I simply want to see the motor run until the pilot decides to shut it down ... now is that so bad!?!

Ken

[Stoney]

I have a couple of the B-24 valves and I'd sell them for $100 shipped.
email me if interested.

[b29flteng]

I've used a GRG grease (Gas Resistant Grease) in fuel valves with good results. It lubricates the cone and also helps to seal any leaks.

Grease, Plug Valve, Gasoline and Oil Resistant, Nato Code Number G-363

[pcm4630]

The teflon cones for the Texans are illegal and extremely dangerous. I nearly lost my beautiful SNJ-5 because a teflon cone had been substitured for the original cork seal by the previous owner. The original cork seals are now virtually impossible to find.

An excellent alternative is the Thompson Products, Inc. part # TCB-14100-1. The functionality and line arrangement are the same, and it's a permanent, lifetime replacement. It's slightly larger than the original part, and will require a slightly modified aluminum mounting bracket. The valve is machined, incorporating O-Rings instead of a cork cone. Approval for standard category Texans should be very easy. I have ten (10) yellow tagged valves available.

Contact:
danp@pcmonline.com
Cell: (918) 630-6760

[SPANNERmkV]

Sort of on the same subject, in that it is fuel system...

Anybody got any suggestions for a fuel Wobble Pump that will not hold prime?
A friend's T-6 is giving him heck.
It has been rebuilt, cleaned, a new gasket cut...

It will work fine 3 or 4 times and then will not work at all.
Our favorite kind of problem- intermittent.
No visible signs of fuel leaks anywhere that can be detected.

SPANNER the facilitator

[Taylor Stevenson]

Spanner,

Was it rebuilt by someone who has successfully rebuilt them in the past? From what I have heard, rebuilding a T-6 wobble pump (D-3? that's off of memory and if I'm right, I'm a nerd) is somewhat of an art form and requires a special touch. It isn't something the owner can disassemble, clean, and throw back together and have work right... without experience or a lot of luck. Somebody disagree, but that's what I've heard... Stoney?

[Stoney]

Don't look at me, all I ever did move the handle alot